This invention relates to sewing apparatus, primarily industrial apparatus employing sewing machines, and in particular to a sandwich synchronizer for interposition between a sewing machine and a rotary encoder used by the sewing machine motor to generate a sequence of pulses as the sewing machine is utilized.
In sewing apparatus, and in particular in industrial sewing apparatus, sewing progresses at a high rate of speed. The sewing apparatus is provided with a motor to drive its sewing mechanism, and typically includes a handwheel extending from and comprising part of a rotatable drive shaft of the sewing apparatus. A rotary encoder having an encoder assembly is attached to the drive shaft for generating a series of pulses as the drive shaft is rotated. There are a number of manufacturers of industrial sewing apparatus, and each produces a rotary encoder different from the other. There is no common rotary encoder or common protocol for output from the rotary encoder, and each manufacturer therefore produces a proprietary design having a unique output.
When the rotation of the drive shaft of the sewing apparatus is to be used for other purposes, such as aiding the determination of a skipped stitch, helping in detecting other stitching irregularities, or simply providing the positioning of the sewing head of the sewing apparatus, the output of the rotary encoder must be translated in some manner to be compatible for the intended purpose. If there were a universal means of determining the speed, direction and position of the drive shaft for the sewing apparatus, regardless of the type of motor or manufacturer, that would be a significant improvement from what is presently available.